Process of polymerization by dielectric heating of unsaturated fatty acids, esters of unsaturated fatty acids, unsaturated hydrocarbons, or unsaturated derivatives of these products.
This invention relates to a process of polymerization of unsaturated fatty acids, esters of unsaturated fatty acids, unsaturated hydrocarbons or esters of unsaturated hydrocarbons, or unsaturated derivatives of these products by dielectric heating, as well as to the polymers obtained and uses of these polymers, that is, heating at microwave frequencies or radio frequencies.
Compounds obtained by polymerization of fatty acids or of esters of unsaturated fatty acids are well known. The polymers obtained on the basis of unsaturated vegetable oil, in particular, may be cited. Polymerization processes make use of double bonds of fatty acids or, after initial treatment (isomerization), conjugate bonds.
Current processes for preparation of these polymers such as blown oils or stand oils are characterized by use of heat (thermal polymerization) in the presence of catalysts (homogenous or heterogenous). Use of catalysts such as oxygen or anthraquinone makes it possible to obtain polymers of high viscosity but ones which are highly reactive after their preparation, a feature of interest only for areas of application such as paints in which the product is required to dry (reticulation phenomenon).
In areas such as lubrication, cosmetics, or pharmacology, on the other hand, there is a demand rather for polymers stable under external restraints (oxygen, water, etc). The restraint of eliminating traces of catalysts is sometimes added in cosmetics and in pharmacology.
Polymers have been developed on the basis of this fact: they are prepared on the basis of triglycerides at least one fatty acid of which comprises at least one unsaturated compound (conjugate or not), preferably without a catalyst and in an atmosphere devoid of oxygen. These developments use processes such as heating belts, gilotherms [heat transfer fluids], or resistors, which processes take much time, something which generally prevents obtaining polymers exhibiting high viscosities; they are also costly because of the investment amounts required.
The invention makes it possible to reduce these major disadvantages. Use of microwaves or radio frequencies yields dual benefits; on the one hand the microwave or high-frequency energy interacts immediately at the molecular level, and on the other less energy is required (it is the molecules themselves which, when polarized by the electric fields of the microwaves or radio frequencies, convert electromagnetic energy to heat).
The applicant has found, as a first feature of the invention, that polymerization of unsaturated fatty acids, of unsaturated hydrocarbons, of unsaturated derivatives of these products, or of a mixture of them by dielectric heating, that is, by means of microwaves or radio frequencies, preferably microwaves, makes it possible to obtain high-viscosity products with more favorable reaction periods.
Hence the invention relates to the general process of polymerization of unsaturated fatty acids, unsaturated fatty acid esters, unsaturated hydrocarbons, and similar products, by dielectric heating, that is, by means of microwave frequencies or radio frequencies, preferably microwaves.
Use of microwave energy in industry is already known, but in a different field and to cope with different problems, especially in the area of epoxy resins and the like.
Microwaves or radio frequencies have not been described for polymerization of products of the kind described above, and of squalene in particular.
Nor has a description been given of the possibility of replacement of use of squalane in cosmetics by a polymer of squalene obtained at lower cost by the process claimed for the invention.
The gain in time and energy combined with lower investment cost permits the assertion that the dielectric heating process is faster and more cost effective.
This invention may be applied for polymerization of unsaturated fatty acids, esters of unsaturated fatty acids, unsaturated hydrocarbons, plant oils, animal oils and fats, and their unsaturated derivatives. These products may be used in raw or refined form, optionally after undergoing preliminary treatment.
The reaction may involve a single reagent or a mixture of reagents in varying proportions.
Polymerization is carried out by subjecting the reagent or reagents to dielectric heating, that is, heating at frequencies ranging from around 30 Ghz to around 3 MHz. Microwave frequencies, which are preferred, range from around 30 GHz to around 300 MHz, preferably 2.45 Ghz (authorized frequency with 2-percent tolerance) or 915 MHz (authorized frequency with 1.4-percent tolerance). The radio frequencies range from around 300 MHz to around 3 MHz, preferably 13.56 MHz (authorized frequency with 0.05-percent tolerance) or 27.12 MHz (authorized frequency with 0.6-percent tolerance).
The reaction temperatures range from 200 to 400xc2x0 C., by preference 230 to 350xc2x0 C., with a temperature rise of three to 60 minutes, by preference three to 20 minutes, over a total reaction period of 15 minutes to 15 hours, preferably 15 to 360 minutes, by preference 15 to 120 minutes, with or without catalyst, preferably without catalyst, under constant agitation, in an inert atmosphere or not, depending on the result desired.
The polymerization reagents for this invention may be chosen from among animal and plant oils and fats and from among the polyterpenes some of which are derived from the oils and fats in question.
Sperm whale oil, dolphin oil, whale oil, seal oil, sardine oil, herring oil, shark oil, cod liver oil, neat""s-foot oil and fats of beef, pork, horse, and sheep (tallow) may be cited as oils or fats of animal origin.
As oils of plant origin one may mention, among others, rapeseed oil, sunflower oil, peanut oil, olive oil, walnut oil, corn oil, soya oil, flaxseed oil, hemp oil, grapeseed oil, coconut oil, palm oil, cottonseed oil, babassu oil, jojoba oil, sesame oil, castor oil, dehydrated castor oil, hazelnut oil, wheat germ oil, borage oil, primrose oil, tall oil.
Use may also be made of the components of animal or plant oils such as scalene extracted from the nonsaponifiable components of plant oils (olive oil, peanut oil, rapeseed oil, corn germ oil, cottonseed oil, flaxseed oil, rice bran oil) or contained in large amounts in shark oil.
As unsaturated fatty acids use may be made, singly or in mixture, as nonrestrictive examples, of one or more of monounsaturated fatty acids such as oleic acid, palmitoleic acid, myristic acid, petroselenic acid, erucic acid, etc; one or more of polyunsaturated fatty acids such as linoleic acid, alpha-linoleic and gamma-linoleic acids, arachidonic acid; one or more of acids comprising conjugate dienes or conjugate trienes such as licanic acid or the isomers of linoleic or linolenic acids; one or more of the acids comprising one or more hydroxyl groups such as ricinoleic acid.
As esters of unsaturated fatty acids use may be made, singly or in mixture, as nonrestrictive examples, of one or more of the esters obtained by esterification between a monoalcohol and/or a polyol (singly or in mixture), and at least one unsaturated fatty acid. As nonrestrictive examples of monoalcohol mention may be made of methanol, ethanol, or butanol; as nonrestrictive examples of polyols, glycerol, sorbitol, neopentylglycol, trimethylpropane, pentaerythritol, glycol, ethylene glycol, polyethylene glycol. Waxes and phospholipids may also be used as fatty acid esters.
As unsaturated hydrocarbons use may be made, singly or in mixture, as nonrestrictive examples, of one or more of the terpenic hydrocarbons, oxygenated or not, that is, one or more isoprene polymer, one or more isobutene polymer, styrene, ethylene, butadiene, isoprene, propene, or one or more of the copolymers of these alkenes.
Unsaturated derivatives of these compounds may be obtained, for example, by activation of residual unsaturated compounds by any method known to the expert, such as hydrogenation, hydroxylation, epoxydation, or sulfonation.
By preference use will be made as reagent or reactive mixture of one or more esters of unsaturated fatty acids or their derivatives comprising at least one unsaturated compound (amides, partially hydrogenated fatty acid esters, polyoxyethylenated fatty acid esters, etc), singly or in mixture with one or more unsaturated hydrocarbons.
The expert will understand that the invention may also be applied to analogous compounds, that is, to ones whose chemical structure authorizes the same action of microwave or radio frequencies with regard to polymerization.
A particularly interesting application of the invention is to be found in relation to squalene or spinacene. What is involved is a precursor of cholesterol found among other places in the liver of sharks. It is known for its highly emollient, antifungal, and antibacterial properties. In addition, it has a nonfat feel, an aspect which would present a real advantage in the area of cosmetic products.
Patent FR 2 576 309, which deals with the refining of paraffins, is known in this context. A manufacturing process described in patent EP 0 228 980 is also known.
Also of the state of the art is hydrogenation of the six double bonds of squalene to produce squalane, which is useful in cosmetology. However, this process is by nature very cumbersome and accordingly presents a problem for industry.
Lastly, use of byproducts resulting from refining of olive oil as a basis to obtain the esters, followed by distillation of the esters to obtain the squalene which may be recovered, is a state-of-the art process.
As is to be seen, squalene and its derivatives have been extensively studied; this is indicative of the value of these products to industry.
As indicated above, these products are of great potential interest in the field of cosmetics. However, if polymerization of squalene to obtain a polymer usable in cosmetics is undertaken, the processes referred to above use very costly heating.
Use of microwaves or high-frequency waves as claimed for the invention in order to polymerize squalene resolves the problems indicated in the foregoing.
A more detailed description is given below of application of the invention.
Squalene or spinacene, of empirical formula C30H80, is a polyterpene having the following developed formula: 
Human sebum contains more than 10 percent of this substance; hence its importance in dermatology and cosmetology. In effect, squalene softens the skin (emollient nature) and participates in its protection (as antibacterial, antifungal). It is a good vehicle for active principles (as an application in dermatology). But cosmetologists make use rather of squalane (hydrogenated squalene) because it is saturated and thus more stable toward oxidation. Hydrogenation of squalene is a costly process which yields little differentiation from traditional hydrocarbons such as oils and paraffin waxes.
As a second and advantageous characteristic of the invention the applicant proposes replacing squalane with squalene, which is polymerized by means of microwave frequencies or radio frequencies, either singly or in combination with one or more unsaturated fatty acids or esters of unsaturated fatty acids or plant or animal oils or other unsaturated hydrocarbons. Since squalane is sometimes replaced with a hydrogenated polyisobutene (unsaturated hydrocarbon), the squalene may be replaced with a polyisobutene without going beyond the scope of the present invention.
These oils and fats of animal or plant origin, as well as their derivatives, may be subjected to preliminary treatment in order to make them more reactive or, on the contrary, less reactive. The invention relates both to an isolated reagent and to a reaction mixture including two or more components or reagents. These reaction mixtures may have components in equal proportions, or some components may be present in higher proportions.
The polymerization is effected by dielectric heating of the reagent or reagent mixture, that is, by heating at microwave frequencies or radio frequencies. The temperature selected ranges preferably from 200 to 400xc2x0 C., especially from 220 to 350xc2x0 C.
Use of microwave frequencies or radio frequencies makes it possible to impose a temperature rise time (that is, the time required for transition from ambient temperature to polymerization temperature) ranging from three to 60 minutes, preferably from three to 20 minutes.
Reduction of the temperature rise time makes it possible to create ideal polymerization conditions for the reagent and thus to reduce the total reaction time but uses more power over a short period.
The total reaction time depends on the reagent or reagents used and on the viscosity it is desired to produce, and ranges preferably from 15 minutes to 15 hours, preferably from 15 to 360 minutes, and by special preference from 15 to 120 minutes. The total reaction time may be reduced by using a higher temperature. However, temperatures which are too high may result in degradation of the products.
Hence a choice will have to be made of a reaction temperature/total reaction time combination which permits optimum polymerization in a short time but without excessive energy consumption and with no risk of degradation of the product. The expert will know how to optimize these parameters by means of routine tests, in accordance with the criteria indicated below.
The polymerization may be carried out with or without catalysts. The catalysts may be homogenous or heterogenous. For example, anthraquinone, sulfur anhydride, or the soluble salts of nickel may be used as homogenous catalysts. Examples of heterogenous catalysts are zeolites or ion exchange resins in acid form. Use will be made preferably of catalysts specially adapted to radio frequencies or microwave frequencies, such as clays of the montmorillonite or bentonite type, which have the effect of increasing molecular interaction when subjected to dielectric heating.
It will be made certain that agitation is sufficient to ensure a uniform temperature in the reaction vessel.
The polymerization may be conducted in a normal or an oxygen-rich atmosphere (for example, for making blown oils), or, preferably in an inert atmosphere (in the presence of nitrogen, argon, helium, or other rare gases employed singly or in mixture). The process is conducted preferably under low pressure, with care taken to renew the atmosphere.
In the case of squalene the invention consists of reducing the number of unsaturated bonds in the polymerizing agent, singly or in mixture with at least one of the reagents cited above, by means of the process mentioned above, this making it possible to obtain an oxidation-stable polymer whose viscosity depends on the degree of polymerization. In this way a second functionality is imparted to the squalene. Hence the polymer obtained, in addition to its emollient aspect, will be consistency factor in cosmetic product formulations. In addition, the polymerization process in question is less costly than the hydrogenation process involving use of costly catalysts.
Polymerization operations may be carried out by batches (discontinuously), but it is advantageous to utilize continuous processes for limited-time reactions.
To halt the polymerization it suffices to lower the reaction mixture temperature so as to keep the latter below the reaction temperature. This depends to a significant extent on the reaction mixture. It is to be noted that use of microwaves or radio waves is of particular advantage at this point in the process because there is no inertia due to the walls of the reaction vessel.
A series of supplementary stages makes it possible to refine the polymer in keeping with the needs of the end user. The neutralization number of the polymer produced may be lowered. The polymer may be deodorized, its moisture content may be reduced, or it may be decolorized.
These refining stages are well known to the expert. A number of them may be mentioned.
Lowering of the neutralization number, which reflects the number of free carboxylic acids present in the polymer, is effected by adding in excess agents selected from among alcohols, epoxides, hydroxides, and glycidyl esters, singly or in combination. The acidity is thus neutralized by synthesizing esters, salts, etc. In order to do this it suffices to lower the temperature of the reaction mixture to the reaction temperature of these esters, salts, etc.
It is to be noted that time Will be gained for this stage thanks to the microwave frequencies or radio frequencies, since the reaction time will range from three minutes to three hours, depending on the polymer, as against five times as long on the average with conventional heating processes.
Deodorization may be effected by steam distillation. This operation is carried out at temperatures ranging from 50 to 240xc2x0 C.
After this stage the moisture content is reduced by conventional heating processes (heating by conventional process to reach the boiling point of water and distillation under vacuum, or use of drying compounds) or, preferably, by using dielectric heating, that is, by using microwave frequencies or radio frequencies which cause water molecules to react and, again, yield a saving of time. The expert will know how to determine the appropriate reduction of the moisture content in accordance with the application considered, for example, a content below 500 ppm is desirable for lubricants.
Whenever the moisture content of the reagent or reagent mixture is considered to be too high, the moisture content is reduced before the polymerization stage is carried out; as described above, use may be made of conventional heating methods or, preferably, dielectric heating. For example, by following this procedure whenever the reaction mixture is made up of esters, one achieves significant reduction in the hydrolysis phenomena responsible for a high neutralization number at the end of polymerization.
Decolorization may be effected by using oxygenated water or by using bleaching earth or by passing the polymer obtained through activated charcoal filters.